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There are few reports of pollen count and identification in Mexico; therefore, it is important to generate more information on the subject. This study was designed to describe the prevalence of pollen in the city of Monterrey, Mexico, during the year 2004. Atmospheric pollen was collected with a Hirst air sampler, with an airflow of 10 L/minute during 2004. Pollen was identified with light microscopy; the average monthly pollen count as well as total was calculated from January 2004 to January 2005. The months with the highest concentration of pollen were February and March (289 and 142 grains/m(3) per day, respectively), and July and November had the lowest concentration (20 and 11 grains/m(3) per day, respectively). Most of the pollen recollected corresponded to tree pollen (72%). Fraxinus spp had the highest concentration during the year (19 grains/m(3) per day; 27.5% of the total concentration of pollen). Tree pollen predominated from January through March; with Fraxinus spp, Morus spp, Celtis spp, Cupressus spp, and Pinus spp as the most important. Weed pollen predominated in May, June, and December and the most frequently identified, were Amaranthaceae/Chenopodiaceae, Ambrosia spp, and Parietaria spp. The highest concentration of grass pollen was reported during the months of May, June, September, October, and December with Gramineae/Poaceae predominating. Tree pollen was the most abundant during the year, with the ash tree having the highest concentration. Weed and grass pollen were perennial with peaks during the year.

The epidemiology of allergic diseases has not been studied extensively in Mexico. The present study, based on the International Study of Asthma and Allergies in Childhood Phase IIIB survey, reports the prevalence of allergic rhinitis and the associated risk factors in the pediatric population in four cities in northern Mexico. Children (6-7 years old) and adolescents (13-14 years old) in public elementary and secondary schools were surveyed in 2002 and 2003. The subjects were chosen randomly from Ciudad Victoria, Mexicali, Monterrey, and Tijuana. The following categories were analyzed: occurrence of rhinitis symptoms (currently or in the last 12 months), rhinoconjunctivitis symptoms, a previous diagnosis of allergic rhinitis, and relevant environmental factors. Factors associated with rhinitis that were identified previously with the chi-squared test were analyzed using logistic regression. The number of valid questionnaires was 10,892 for schoolchildren and 12,299 for adolescents. In 6- to 7-year-old children, the following frequencies were determined: rhinitis (ever), 27.9%; current rhinitis, 24.2%; rhinoconjunctivitis, 9.2%; and diagnosis of allergic rhinitis, 5.5%. The corresponding frequencies in 13- to 14-year-old children were 33.3, 34.1, 18.4, and 3.8%. In both 6- to 7-year-old and 13- to 14-year-old children, all rhinitis items were associated with asthma symptoms, dermatitis symptoms, paracetamol consumption, and maternal smoking (odds ratio, >1; p < 0.05). The main risk factors associated with allergic rhinitis symptoms in children and adolescents from cities in northern Mexico were other allergic conditions, paracetamol consumption, and passive smoking.